Bi4Ti3O12 Phase Research Articles

Innovative binary Na0·5Bi0·5TiO3-based composite ceramics with excellent comprehensive energy storage performances under low electric fields

The insufficient energy storage properties (ESPs) of lead-free dielectric ceramics at low electric fields (E) hinder their applications in the integrated and miniaturized electronic equipment. From this perspective, a synergetic tactic for enhancing the ESPs of (1-x) (Na0·5Bi0.5)0.75Sr0·25TiO3-xCa(Mg1/3Ta2/3)O3 ceramics at low E is proposed by constructing composite ceramics in combination with the design of average ionic polarizability. Consequently, the best recorded ESPs (recoverable energy density Wrec ∼ 6.7 J/cm3 and energy efficiency η ∼ 92.5 %) contrasted to other lead-free ceramics at the same E (260 kV/cm) are attained in the x = 0.15 ceramics. This is owing to the improved breakdown E caused by the second phase Bi4Ti3O12 and the retentive high-polarization characteristic of matrix. In addition, rapid discharge time (∼66.8 ns), excellent thermal (30–130 °C) and frequency (1–100 Hz) stability are also achieved. Hence, the present work offers an innovative insight into the optimization of comprehensive ESPs for dielectric ceramics at low E.

Preparation of Bi4Ti3O12/TiO2 by flame spray pyrolysis for photoelectrocatalytic degradation of tetracycline

The negative effects of the irrational use of antibiotics have been increasing attention from the public, making it urgently needed to develop effective techniques for removing antibiotics from wastewater. Simultaneously, the construction of heterogeneous TiO2 photoanodes can be used to enhance photoelectrocatalytic performance. Herein, we used an advanced method, namely one-step flame spray pyrolysis (FSP) to in-situ prepare Bi4Ti3O12/TiO2 heterostructures. The ultra-high temperature characteristics of this method facilitated the high dispersion of Bi species on TiO2, leading to the formation of the Bi4Ti3O12 phase within milliseconds. Bi4Ti3O12 forms a “Z" type heterojunction with TiO2, improving charge separation and enhancing electron transfer efficiency. The photoeletrocatalytic degradation effect of Bi4Ti3O12/TiO2 on tetracycline is significantly improved. Under simulated sunlight irradiation for 75 min and 1V voltage, the removal of tetracycline can reach 99.7%. The recycling degradation experiments demonstrated the remarkable reusability and stability of Bi4Ti3O12/TiO2, while the evaluation of degradation intermediates and toxicity analysis of tetracycline were also conducted. Furthermore, free radical trapping experiments confirmed that hydroxyl radicals and holes play a significant role in the removal of tetracycline.

Achieving high energy storage density and efficiency in (Na0.5Bi0.5)TiO3-based lead-free ceramics

Due to the demands of miniaturization, weight reduction and green development for electronic devices, development of lead-free dielectric ceramic capacitors with high recoverable energy density (Wrec) and energy storage efficiency (η) attracts much attention. To this end, (1-x)[0.75(Na0.5Bi0.5)TiO3-0.25SrTiO3]-xNdNbO4 (abbreviated as: NBST-xNN) ceramics were fabricated through a solid-state reaction method. After adding NN, the non-perovskite phase of Bi2Ti2O7 (BTO) with low dielectric constant (εr) and loss (tan δ) is generated. Finite element software (COMSOL) was used to explore the influence of the BTO phase on breakdown strength (Eb). The simulation result indicates that the BTO phase with a low εr concentrates a larger local electric field (LEF), and thus weakens the LEF loading in the main perovskite phase, which is beneficial for enhancing Eb. Moreover, NN doping significantly decreases the oxygen vacancy concentration in NBST ceramics, which plays a key role in improving Eb. On the other hand, as NN content increases, the hysteresis of the polarization (P)-electric field (E) loops is substantially suppressed, and the polarization saturation is delayed, which can be ascribed to the appearance of the BTO phase having a linear dielectric characteristic and to the enhanced fluctuations of composition and charge by NN doping. Benefitting from the above factors, the optimal energy storage performance (ESP) with a Wrec of 4.14 J/cm3 and an η of 90 % is obtained in NBST-0.08NN ceramics. Meanwhile, the ESP of NBST-0.08NN ceramics shows good charge-discharge properties and thermal stability. In conclusion, these results demonstrate that NBST-0.08NN ceramics are promising candidates as environment-friendly dielectric capacitor materials.

Oxygen vacancies-modified S-scheme heterojunction of Bi-doped La2Ti2O7 and La-doped Bi4Ti3O12 to improve the NO gas removal avoiding NO2 product

Monoclinic phase La2Ti2O7 and orthorhombic phase Bi4Ti3O12 with layered crystal structure constructed by the perovskite slab were widely used in photocatalysis. Their electronic structures are the most crucial factor in high photocatalytic activity. Bi-doped La2Ti2O7 gradually converts to La-doped Bi4Ti3O12 with the incorporation of bismuth ions, and the two phases build an S-scheme heterojunction. More oxygen vacancies were introduced into the S-scheme heterojunction after heat treatment in a nitrogen atmosphere. The 0.1BTO/LTO-OV sample exhibits the largest NO removal efficiency of 52% and only 5.6 ppb NO2 intermediate generation. The improved NO removal efficiency was ascribed to the synergistic effect of oxygen vacancies, doping and heterojunction, providing a new insight into the photocatalytic NO removal. The photocatalytic mechanism was eventually proposed on the basis of trapping experiments.

Effects of B2O3-Bi2O3 addition on the dielectric properties of low-temperature-sintered MgO-TiO2(w) ceramics

The effects of different contents of B2O3-Bi2O3 on the sintering temperature and dielectric properties of MgO-12%TiO2(w) ceramics were investigated. B2O3-Bi2O3 addition effectively reduced the sintering temperature and improved the dielectric properties of ceramic samples; however, an excessive amount of B2O3-Bi2O3 led to the deterioration of dielectric properties. This is because Bi2O3 participated in the chemical reaction between MgO and TiO2 and generated a high-dielectric-loss Bi2Ti2O7 phase, resulting in an increased dielectric loss in the ceramic samples. In contrast, B2O3 formed a liquid phase to fill the grain gaps and pores during sintering, improving the densities of the ceramic samples. An appropriate amount of B2O3-Bi2O3 accelerated the reaction between MgO and TiO2 and formed ultralow-dielectric-loss phases—MgTiO3 and Mg2TiO4, and the dielectric losses of the ceramic samples decreased to an order of 10−5.

Effect of Li2CO3–Bi2O3 doping on the low-temperature sintering, structure, and dielectric and mechanical properties of MgO–TiO2(w) ceramics

Dense MgO–12% TiO2(w) ceramics containing 12 wt% TiO2, which were doped with Li2CO3–Bi2O3 composite sintering aids, were prepared at a low sintering temperature of 950 °C in this study. The effects of sintering additives on the sintering characteristics, phase composition, microstructure, and dielectric and mechanical properties of the ceramic samples were systematically investigated, and the influences of their phase composition and microstructure on the dielectric and mechanical properties were examined. The introduction of sintering aids produced a new Bi4Ti3O12 phase in the sample structure, while the residual Bi2O3 mixed with the newly formed Mg2TiO4 and Bi4Ti3O12 phases distributed at MgO grain boundaries formed a structure surrounding MgO grains. This structure filled the pores in the ceramic sample, which increased its density and enhanced the mechanical properties. At a Li2CO3–Bi2O3 content of 15 wt%, the density, flexural strength, and Vickers hardness of the ceramic samples reached their maximum values of 3.4 g/cm3, 218.9 MPa, and 778.7 HV, respectively. However, the further increase in the Li2CO3–Bi2O3 content deteriorated their dielectric properties although the dielectric constant and dielectric loss remained below 13.4 and 2.1 × 10−3, respectively. The findings of this work indicate that Li2CO3–Bi2O3 sintering aids can significantly lower the sintering temperature of MgO–12% TiO2(w) ceramics and control their dielectric and mechanical properties through microstructural changes.

Novel strategies to tune the color emission of Bi2Ti2-xZrxO7:Er3+,Yb+3 upconversion phosphors: Substituting Ti by Zr and annealing at high temperatures

Bi2Ti2-xZrxO7:Er3+,Yb3+ phosphors were synthesized with different content of Zr (X = 0–1.5) by combustion method at 550 °C, producing a mixture of Bi2Ti2O7/Bi4Ti3O12 phases. After increasing the synthesis temperature to 1000 °C, a pure Bi2Ti2O7 (BiTiO) phase was obtained as well as porous coalesced microparticles (2–10 µm) with pore sizes of 110–420 nm. Those samples produced green (548 nm)/red (655 nm) and NIR (1530 nm) emission bands after excitation with 980 nm and their color emission was tuned from green to yellow–red or viceversa using two strategies: i) by increasing the Zr content in the Bi2Ti2-xZrxO7:Er3+,Yb3+ host (from X = 0 to 1) or ii) by increasing the synthesis temperature from 550 to 1000 °C. Interestingly, the intensity of the NIR and red emission bands was enhanced with the content of OH groups on the surface of the BiTiO:Yb,Er phosphors.

Microstructure and ferroelectric properties of Ta-doped Bi3.25La0.75Ti3O12/ZnO thin film capacitors

Ta-doped Bi3.25La0.75Ti3O12(BLTT)/ZnO films were fabricated on Pt(111)/Ti/SiO2/Si substrates by a magnetron sputtering method. Firstly, ZnO crystal thin films were grown on the substrates by a reactive sputtering method. Then, BLTT thin films were deposited on the ZnO layers at room temperature and post-annealed at 600 °C. The micromorphology, ferroelectric and dielectric properties of BLTT/ZnO films were analyzed. The XRD analysis shows that ZnO buffer layer significantly reduces the crystallization temperature of BLTT thin film. The TEM results show that lamellar BLTT grains are grown on ZnO layer at a certain angle with few elements diffusion at the interface of ZnO phase and Bi4Ti3O12 phase. The ferroelectric properties indicate that BLTT/ZnO films exhibit different remanent polarization and coercive fields under electric field with different directions. The novel mechanism of tailoring ferroelectric properties may open new possibilities for designing special ferroelectric devices.

Non–ferroelectric intercalation structure based on Aurivillius phase Bi4Ti3O12: A research arena to achieve high energy storage performance

High density energy capacity is the benchmark of electronic industry, and its improvement is on the way. Here, the BaCaBi4Ti5O18 films present high efficient energy storage trait, which is originated from ferroelectric/non–ferroelectric intercalation structure. The emergent of large gradient elastic energy in ferroelectric/non–ferroelectric intercalation structure not only crushes the ferroelectric domains, but also modulates space charges accumulation. Both factors contribute to the high polarization and intense breakdown strength. The contrast experiments were conducted by single ferroelectric intercalated structure Bi5Ti3FeO15 films, which show almost non ferroelectric energy storage behavior. The finite element simulations are consistent with the experimental evidences. The present results may facilitate a way for structural design of Aurivillius family, which is capable of acting as remarkable energy storage tasks.

Structure and dielectric properties of (1-x)Bi0.5Na0.5TiO3-xBaTiO3 piezoceramics prepared using hydrothermally synthesized powders.

The influence of different processing parameters and various Ba2+ addition (up to 10 mol%) on the structure and dielectric properties of Bi0.5Na0.5TiO3-BaTiO3 (BNT-BT) ceramics was investigated. The powders were hydrothermally synthesized in the alkaline environment at 180°C for different time periods. X-ray diffraction confirmed the presence of dominant rhombohedral Bi0.5Na0.5TiO3 phase and a small amount of secondary pyrochlore Bi2Ti2O7 phase in the pure BNT powders. In addition, one-dimensional Na2Ti2O7 structure was also observed in the powder hydrothermally treated for a long time (i.e. 48 h). The amount of secondary pyrochlore phase in the BNT-BT powders increases with the increase of Ba2+ content. The synthesized powders were pressed into pellets and finally sintered at various temperatures up to 1150°C. High density (more than 90%TD) was obtained in all BNT-BT sintered samples. Optimal sintering parameters were chosen in order to obtain dense ceramics with the optimal phase composition. The temperature dependence of dielectric properties for the BNT-BT ceramics was also studied. Relaxor behaviour of BNT-based ceramics and broad transition peaks are evident in all samples. Dielectric constant up to 400 as well as an acceptable low dielectric loss at temperatures lower than 200°C were obtained in BNT-BT ceramics.

Photocatalytic Properties of Bi2-xTi2O7-1.5x (x = 0, 0.5) Pyrochlores: Hybrid DFT Calculations and Experimental Study.

The photocatalytic properties of Bi2-xTi2O7-1.5x (x = 0, 0.5) pyrochlores are examined via ab initio calculations and experiments. A coprecipitation method is applied for the synthesis of nanopowder pyrochlores. The pyrochlore phase formation starts at 500 °C (Bi2Ti2O7) and 550 °C (Bi1.5Ti2O6.25). Nanopowders are found to be a metastable character of pyrochlore phases. The presence of bismuth and oxygen vacancies enhances the thermal stability of the Bi1.5Ti2O6.25 phase in comparison with the Bi2Ti2O7 phase. The estimated crystallite size is 30-40 nm with noticeable agglomerates of about 100-300 nm according to scanning electron microscopy (SEM) and with the formation of particles (510-580 nm) in the aqueous medium. The isoelectric points of the nanopowders seem to be shifted to the strongly acidic region, resulting in the formation of negative surface particle charges of -33 mV (Bi2Ti2O7) and -27 mV (Bi1.5Ti2O6.25) at pH 5.88 in distilled water. The specific surface area is 11.5 m2/g (Bi2Ti2O7) and 12.00 m2/g (Bi1.5Ti2O6.25). The use of the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional allows achieving an excellent agreement between theoretical and experimental structural parameters. The screened Coulomb hybrid HSE03 functional is the most appropriate for describing the optoelectronic properties. Bismuth titanate pyrochlores are wide-gap semiconductors with strong abilities to be active photocatalysts under visible irradiation. The optical Eg values for direct/indirect transition according to the experiment, 3.19/2.94 eV (x = 0) and 3.24/3.03 eV (x = 0.5), and the DFT/HSE03 calculations, 2.92/2.87 (x = 0) and 3.42/- eV (x = 0.5), are in the visible light region and are close. The calculated low effective masses of the charge carriers and suitable band edge positions confirm the ability of the pyrochlores to act as photocatalysts. The photocatalytic activity has been evaluated through the decomposition of rhodamine B under visible irradiation. Bi2Ti2O7 shows the highest activity in comparison with Bi1.5Ti2O6.25, which is in good agreement with theoretically predicted and experimentally revealed characteristics.

Sintesis Bi4Ti3O12 Terdoping Vanadium dengan Metode Lelehan Garam Tunggal NaCl

Bi4Ti3O12 merupakan senyawa Aurivillius lapis 3 yang berpotensi sebagai material fotokatalis dengan energi celah pita 2,9 eV (427 nm). Untuk memperluas pemanfaatannya, maka energi celah harus diturunkan. Salah satu usaha untuk menurunkan energi celah pita adalah dengan teknik pendopingan logam. Dalam penelitian ini, kami melakukan pendopingan logam vanadium pada Bi4Ti3O12 (Bi4Ti3-xVxO12 (x= 0, 0,05; 0,1; 0,15, dan 0,2)) dengan metode lelehan garam. Data difraktogram menunjukkan fasa Bi4Ti3O12 terbentuk dengan fasa pengotor BiNaO3 dan NaV6O11. Hasil karakterisasi dengan menggunakan Scanning Electron Microscopy (SEM) menunjukkan bahwa bentuk partikel Bi4Ti3O12 adalah plate-like. Hasil karakterisasi dengan menggunakan ultraviolet (UV)-visible (Vis) Diffuse Reflectance Spectroscopy (UV-Vis DRS) menunjukkan bahwa sampel yang diperoleh mempunyai energi celah pita yang lebih rendah dibandingkan dengan Bi4Ti3O12. Kata kunci: Bi4Ti3O12, dopant vanadium, energi celah

Microstructure and ferroelectric properties of bi-excess Bi4Ti3O12 thin films grown on Si and Pt/Ti/SiO2/Si substrates

Bismuth layer-structured ferroelectric Bi4Ti3O12 thin films have been deposited on n-type Si(111) and Pt(111)/Ti/SiO2/Si substrates using rf-magnetron sputtering process. The effects of substrates and annealing treatments on microstructure and ferroelectric properties were investigated. Scanning electron microscopy and X-ray diffraction patterns exhibited that the as-deposited thin films were noncystalline and transformed to crystalline Bi4Ti3O12 phase with a second phase of Bi12TiO20 after annealed at 700 °C. Ferroelectric properties showed that as-deposited thin film in metal-ferroelectric-semiconductor capacitor form and annealed thin film in metal-ferroelectric-metal form exhibited typical ferroelectric behaviors, wherein the values of remnant polarization were around 0.8 µC/cm2 and 4.8 µC/cm2, respectively.

Differences of Characteristics and Performance with Bi3+ and Bi2O3 Doping Over TiO2 for Photocatalytic Oxidation Under Visible Light

Bi-doped TiO2 photocatalysts were synthesized by sol with a high-pressure hydrothermal method and developed for the photocatalytic degradation of formaldehyde under the visible light irradiation and ambient temperature. According to characterization, some Bi-doped TiO2 can be transformed into the distinctive crystals phase of Bi4Ti3O12, which was crucial for improving activity. The excess Bi2O3 doping into TiO2, such as Bi2O3–N/TiO2 and Bi2O3–C/TiO2, generated a mixed oxides with Bi2O3 and Bi4Ti3O12, was not beneficial to increase the activity of HCHO oxidation, whereas Bi3+/TiO2 composed of TiO2 and Bi4Ti3O12 displayed a higher activity with good stability. It is noteworthy that Bi3+/TiO2 didn’t show the lowest binding energy. However, it exhibited a lower PL intensity, higher adsorption, and activity due to the uniform particulates, high surface areas, and the strong interaction between TiO2 and Bi4Ti3O12, attributing to create superoxide radical anion (.O2−) and hydroxyl radical (.OH). The present results of Bi3+/TiO2 indicated that HCHO could be effectively oxidized from 1.094 to 0.058 mg/m3 (94.7%) under visible light irradiation within 36 h. The current research made effort to draw out the existing state of Bi, which can be better, Bi3+ or Bi2O3, doped in the TiO2.

Processing, phase analysis and microwave dielectric properties of Sr5−xBixTi1+xNb4−xO17 (x = 4, 3) ceramics

The ceramics in Sr5−xBixTi1+xNb4−xO17 (x = 4, 3) series were prepared using solid state sintering method. The phase and microwave dielectric properties were investigated. The parent phase Sr2Bi3Ti4NbO17 and SrBi4Ti5O17 phases did not formed along the Sr5−xBixTi1+xNb4−xO17 series for the compositions with x = 3 and 4. The SrBi4Ti4O15 phase formed as the major phase along with some secondary Bi2Ti2O7 and SrTiO3 phases for the composition with x = 4 in Sr5−xBixTi1+xNb4−xO17 series. For the composition with x = 3 in Sr5−xBixTi1+xNb4−xO17 series, Nb based Bi2Ti2O7 pyrochlore phase formed as the major phase along with SrBi3Ti2NbO12 phase as a secondary phase. In this study, good combination of microwaves dielectric properties i.e., er ~ 166, Qufo 8888 GHz and τf ~ 3.4 ppm/°C is obtained for the compositions with x = 4 sintered at 1200 °C and er ~ 88, Qufo~ 12,500 GHz and τf ~ − 9.36 ppm/°C is obtained for the composition with x = 3 sintered at 1200 °C.

The influence of preparation parameters on the photocatalytic performance of mixed bismuth titanate-based nanostructures

The interesting results about the influence of the preparation technology on the structural properties, surface morphology, and consequent photocatalytic activity of the mixed heterogeneous bismuth titanate-based (BTO) nanostructures have been reported. The XRD, TGD/DTA, UV–Vis, EDX, SEM, and BET analyzes were used to investigate structural, thermal, optical properties, purity, surface morphology, surface and porosity areas. The results of the XRD of the samples prepared by microwave-assisted method(S1) confirms the formation of mixed crystalline phase of BiTi3O12 and Bi12TiO20 nanostructures and also the XRD results of the sample prepared by hydrothermal using autoclave system(S2) shows the formation of mixed crystalline phase of Bi4Ti3O12 and Bi2O3. The results of the photocatalytic activity of the prepared nanostructures showed that the S1 nanostructure was able to remove 98% methylene blue in 28 min and S2 nanostructure was able to remove 98% methylene blue in 40 min.

Thickness-dependent microwave dielectric and nonlinear optical properties of Bi0.5Na0.5TiO3 thin films

Abstract Lead-free Bi0.5Na0.5TiO3 (BNT) films were grown on Pt(111)/Ti/SiO2/Si and quartz substrates for various thickness by using pulsed laser deposition technique. The impact of thickness on structural, microstructural, Raman-spectroscopy, microwave dielectric and nonlinear optical properties have been investigated in detail. X-ray diffraction pattern of BNT films deposited at 700 °C showed rhombohedral crystal symmetry with a small secondary phase of Bi4Ti3O12 and also revealed that the lattice parameters, lattice volume, strain and crystallite size were enhanced with film thickness. The film thickness, refractive index and optical bandgap have been determined by Swanepoel's envelope method and Tauc relation and are in the range of 208 nm–1300 nm, 3.79 eV–3.28 eV and 2.41–1.80, respectively. The third order nonlinear optical properties of films were estimated by Z-scan technique and the 208 nm film exhibited strong nonlinear refractive index (n2 = 4.62 × 10−6 cm2/W) and nonlinear absorption coefficient (β = 0.796 cm/W). The enhancement in microwave dielectric properties was observed with film thicknesses which were measured by using SPDR technique. The leakage current density exhibited the space charge limited current conduction behavior. The enhanced microwave dielectric and nonlinear optical properties of BNT films are promising for microwave tunable and nonlinear photonic device applications.

Combustion synthesis, characterization and photocatalytic application of CuS/Bi4Ti3O12 p-n heterojunction materials towards efficient degradation of 2-methyl-4-chlorophenoxyacetic acid herbicide under visible light

In this study, a series of CuS/Bi4Ti3O12 p-n heterojunction materials were synthesized by a two-step process. Initially, the Aurivillius phase Bi4Ti3O12 (BT) was synthesized by a facile combustion route using urea as a fuel. The Bi4Ti3O12 was subsequently modified by deposition of CuS (5–20 wt%) using a hydrothermal route to prepare the heterojunction materials. The methods of synthesis and calcination temperature were important factors which influenced the morphology, particle size and phase purity of Bi4Ti3O12 material. Phase pure BT nanoplates with planar dimension of 150–200 nm and thickness between 50 and 70 nm were obtained at a calcination temperature of 600 °C. Pure CuS prepared by hydrothermal method, contained hierarchical microspheres with diameter in the range of 1.2–1.6 μm. The heterostructure materials exhibited hierarchical flower like structure consisting of ultrathin CuS nanosheets and BT-nanoflakes. HRTEM and microstructural study revealed microscopic close interaction between the two phases. The optical and electrical measurement study suggested significant improvement in visible light absorption (400–800 nm) and charge carrier separation due to heterojunction formation. The CuS/Bi4Ti3O12 materials showed excellent photocatalytic activity for aqueous phase degradation of 2-methyl-4-chlorophenoxyacetic acid (MCPA) herbicide under visible light (>95% degradation in 3 h). The rate constant for CuS/Bi4Ti3O12 materials was 4.5 times higher than the pure BT material towards MCPA degradation. The OH and O2– radicals have been identified as the reactive species, the formation of which was confirmed by spectrometric method using terephthalic acid and nitroblue tetrazolium as molecular probes. The mechanism of MCPA degradation over the photocatalyst surface has also been elucidated using LC-ESI-MS, TOC and scavenger experiments.

Influence of tantalum on mechanical, ferroelectric and dielectric properties of Bi-excess Bi3.25La0.75Ti3O12 thin film

The Bi-excess Bi3.25La0.75Ti3O12 (BLT) and Bi3.25La0.75Ti2.91Ta0.09O12 (BLTT) thin films were deposited on Pt(1 1 1)/Ti/SiO2/Si substrates using rf-magnetron sputtering method. The effect of tantalum on mechanical, ferroelectric and dielectric properties of BLT thin films was investigated. XRD patterns reveal that BLT and BLTT thin films have a same second crystalline phase Bi12TiO20, but the former has a randomly oriented major Bi4Ti3O12 phase while the major phase in the later is preferentially oriented along 〈1 1 7〉 direction. XPS analysis shows that the substitution of Ta5+ has a significant influence on Ti3+ defects. Mechanical response of thin films is discussed in the light of nano indentation analysis which shows that both the hardness and modulus are reduced with the addition of Ta5+. Ferroelectric properties were improved significantly by Ta5+ doping due to the reduction of Ti3+ defects, and an enhanced remnant polarization (2Pr) of 32.5 μC/cm2 and a decreased coercive field (2Ec) of 260 kV/cm were obtained. In addition, the Ta substitution elevated the dielectric constant and slightly raised the Curie temperature.

Rapid microwave-assisted sol-gel synthesis and exceptional visible light photocatalytic activities of Bi12TiO20

Crystalline Bi12TiO20 and Bi4Ti3O12 particles were selectively synthesized by rapid microwave-assisted sol-gel method. During the thermal decomposition process of the dried gel, microwave calcination played a key role in producing single phase Bi12TiO20. Our Bi12TiO20 demonstrated one of the highest visible-light photocatalytic activities for MO degradation among the reported bismuth titanate particles with various compositions. Single phase Bi4Ti3O12 can also be prepared by either a conventional calcination at high temperature or a combined heat treatment of a conventional heating followed by microwave calcination. The photocatalytic reaction rate constant of the Bi4Ti3O12 prepared by microwave calcination was three times higher than that of conventionally calcined Bi4Ti3O12, further confirming the advantage of microwave calcination in preparation of highly photocatalytically active bismuth titanate.